Income Taxes - Reconciliation Between Effective and Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal income tax rate	21.00%	34.00%
Research and development tax credits	6.00%	3.00%
Non-deductible executive compensation	(1.00%)	0.00%
Valuation allowance	(12.00%)	304.00%
Impact of tax reform	0.00%	(101.00%)
Expired tax attribute carryforwards	(17.00%)	(240.00%)
Gain on branch liquidation	3.00%	0.00%
Foreign currency gains and losses	2.00%	0.00%
Other	(2.00%)	0.00%
Net effective tax rate	0.00%	0.00%

Effective Income Tax Rate Reconciliation, Expired Tax Attribute Carryforwards, Percent

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Effective Income Tax Rate Reconciliation, Gains (Losses) On Foreign Exchange

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to disposition of a business not qualifying as a discontinued operation.

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